Mobile terminals such as smart phones, tablet PCs and notebook computers have been prevalent. A mobile terminal includes a flat display device using liquid crystal or organic EL elements. The display device is connected to a host device which outputs image data, commands, and the like. The display device includes a display panel and a driver processing commands and driving the display panel.
In the display device, pixels two-dimensionally arrayed on the display panel include a common electrode and a pixel electrode, and the liquid crystal or organic EL elements are arranged between the common electrode and the pixel electrode. When the driver writes a pixel signal to the pixels on the display panel, the liquid crystal or organic EL elements arranged between the common electrode and the pixel electrode are controlled and an image is thereby displayed.
Display devices capable of detecting an inputting object such as a finger and a touch pen (also called a stylus) approaching or contacting the screen have been widely employed. The operation of allowing the inputting object to approach or contact the screen is called a touch operation or a touch, and the detection of a position of the inputting object is called touch detection. Examples of the touch detection include various types such as an optical type, a resistive type, a capacitive type, and an electromagnetic induction type. The capacitive type utilizes a feature that the electrostatic capacitance between a pair of electrodes (called a drive electrode and a detection electrode) is varied by approach or contact of the inputting object, and has benefits that the structure is comparatively simple and that the power consumption is small.
If the number of drive electrodes and the detection electrodes is increased to improve the performance of the image display operation and the touch detection operation, in the display device with the touch detection function, a layout of lines connected to the electrodes or a terminal layout of a semiconductor chip controlling the image display operation and the touch detection operation becomes complicated. In accordance with this, the number of terminals of the semiconductor chip is increased, the size of the semiconductor chip becomes larger, and the structure becomes complicated.